1. Technical Field
The present disclosure relates to ultrasonic surgical apparatus for fragmenting and aspirating tissue. More specifically, the present disclosure relates to aspirating tools suitable for use in an ultrasonic surgical apparatus for aspirating tissue and to a method of manufacturing such aspirating tools.
2. Background of Related Art
Devices which effectively utilize ultrasonic energy for a variety of applications are well-known in a number of diverse arts. The application of ultrasonically vibrating surgical devices used to fragment and aspirate unwanted tissue with significant precision and safety has led to the development of a number of valuable surgical procedures. Accordingly, the use of ultrasonic aspirators for the fragmentation and surgical removal of tissue from a body has become known. Initially, the technique of surgical aspiration was applied for the fragmentation and removal of cataract tissue. Later, such techniques were applied with significant success to neurosurgery and other surgical specialties where the application of ultrasonic technology through a handheld device for selectively removing tissue on a layer-by-layer basis with precise control has proven feasible.
Typically, ultrasonic surgical devices for fragmenting and aspirating tissue include an ultrasonic transducer supported within a handpiece, an ultrasonically vibrating tool, an extender connecting the tool to the ultrasonic transducer and a sleeve or flue positioned about the tool. The tool includes a longitudinally extending central bore having one end located adjacent a distal tip and a second end located adjacent the proximal end of the tool. The proximal end of the tool is adapted to engage a vacuum source to facilitate aspiration of fluid. The flue is positioned about the tool to define an annular passage. Irrigation fluid is supplied through the annular passage around the tip to the surgical site where it mixes with blood and tissue particles and is aspirated through the bore in the tool. By mixing the irrigation fluid with the blood and tissue particles, coagulation of the blood is slowed down and aspiration thereof is aided. U.S. Pat. Nos. 5,015,227 and 4,988,334 disclose such ultrasonic surgical devices and are hereby incorporated by reference.
In any surgical procedure, it is necessary that a surgeon be afforded good visibility of the surgical site. Thus, it is important that the ultrasonic tool and flue be configured and dimensioned not to obscure visibility at the surgical site. One problem associated with manufacturing small diameter tools for the above-described ultrasonic surgical devices is machining an even smaller throughbore in the tool. Presently, tools with throughbores having diameters as small as 0.062 inches are known. Efforts to consistently manufacture ultrasonic tools having smaller diameter throughbores have not proven feasible.
Ultrasonic tools having large diameter throughbores are also advantageous during certain surgical procedures. For example, where highly compliant tissue mixed with blood is aspirated, there is increased likelihood of occlusion of the aspiration conduit due to the coagulation of the blood. To make matters worse, ultrasonic vibration of the tool acts to increase the rate of coagulation of the blood within the tool.
One problem associated with manufacturing ultrasonic tools having large diameter throughbores is that the threaded connector on the tool must be dimensioned to be attached to the same handpiece to which the small diameter tools are to be attached. Therefore, in large diameter tools, there is less material between the base of the threads on the threaded connector at the proximal end of the tool and the throughbore. As a result, the fracture rate of the large diameter ultrasonic tools is substantially higher than that of small diameter ultrasonic tools in the area of the threads.
Accordingly, a need exists for improved ultrasonic tools for use with apparatus for ultrasonically fragmenting and aspirating tissue and improved methods of manufacturing such ultrasonic tools which are more resistant to stress fracture and which have smaller diameter throughbores.
In accordance with the present disclosure, an ultrasonic surgical apparatus is disclosed for fragmenting and aspirating tissue. The apparatus includes a handpiece which encloses a transducer having a magnetostrictive or piezoelectric stack. An aspirating tool having a throughbore is connected to the transducer by a connector body. A manifold having an irrigation port is positioned about the aspirating tool. During a surgical procedure, irrigation fluid is supplied through the irrigation port into manifold to the distal end of the aspirating tool, where the irrigation fluid mixes with fragmented tissue and blood from the surgical site. The blood and tissue are removed from the surgical site via the throughbore in the aspirating tool.
The handpiece is adapted to receive a plurality of different size aspirating tools. One such aspirating tool includes a throughbore having a diameter of about 0.045 inches. In order to form such a small diameter throughbore, a two-step drilling process is used. During the first step a proximal portion of the throughbore is drilled using a drill bit having a diameter of 1.25-2.5 times the desired bore diameter. During the second step, a distal portion of the bore is drilled to the desired diameter. The transition between the proximal and distal portions of the throughbore is positioned at a node.
Another aspirating tool adapted for use with the handpiece includes a throughbore having a diameter of preferably about 0.104 inches. During manufacturing, the aspirating tool is machined, the throughbore is drilled, and the proximal end of the tool is threaded. Next, the threads are masked and the aspirating tool is titanium nitride coated. By masking the threads prior to titanium nitride coating, stress concentrations formed in the threads are eliminated.